[MLS] Western Conference teams defended better in 2009 than those in the East. Soccer America's Ridge Mahoney explains why and grades the central defenses of MLS Western Conference teams going into the 2010 season.

Chivas USA's signing of Costa Rican international defender Michael Umana should make it even tougher to score against one of the Western Conference’s perennial contenders.

Chivas USA and four other Western teams -- Los Angeles, Houston, Seattle and champion Real Salt Lake -- conceded 35 goals or fewer last season; of the Eastern teams, only Columbus and Chicago dipped under that benchmark. All five of those Western teams made the playoffs, and two reached MLS Cup.

Successful defending requires more than a solid pairing in the middle, yet numerous mistakes – failing to contest a cross at its origin, a missed tackle in the defensive third, a flapping keeper caught in no man’s land – can be rectified by a decisive centerback, or better yet, two of them.

Rosters are not yet set, but with about a week to go before the opening game, here’s a quick rundown as how the Western teams look in central defense:

SEATTLE. The Sounders tied with Houston for fewest goals conceded (29) with Tyrone Marshall and Jhon Kennedy Hurtado, bolstered by Pat Ianni, in the middle. Converting Hurtado’s loan into a transfer solidifies the starting duo, though Marshall turns 36 this year and with the Concacaf Champions’ League looming will need occasional breaks. Grade:A-

HOUSTON. A move of Geoff Cameron from central defense to midfield leaves Bobby Boswell and Eddie Robinson as the preferred pairing. Robinson missed nearly the entire 2009 season recovering from microfracture surgery on his knee; when he and Boswell were paired together for most of 2008, Houston conceded the fewest goals in MLS. Also on hand is Ryan Cochrane, who started 49 games during the Dynamo’s 2006 and 2007 championship seasons. Grade:B+

LOS ANGELES. Another solid year for Rookie of the Year Omar Gonzalez and Gregg Berhalter can anchor the Galaxy, which has brought in three young Brazilians -- two of them defenders -- on loan after looking a bit old in last year’s playoffs and might need some time to meld youth and experience. Grade: B+ REAL SALT LAKE. In their second season together, Nat Borchers and Jamison Olave forged a good understanding. After a shaky start to the playoffs their anticipation and toughness led a strong effort that allowed just one goal in the last 285 minutes of play. They may be a bit short on pace but they’re good. Ex-Wizard Raushawn McKenzie, a rookie in 2009, has been added to the mix. Grade: B.

CHIVAS USA. The signing of Michael Umana probably means the end of Claudio Suarez’s playing career, and the start of a potentially excellent duo: Umana, age 27, alongside quick, strong, skilled, young (20) Colombian Yamith Cuesta, who is still on loan. Left back Jonathan Bornstein, who has also played in the middle the last nine months for club and country, gives this position incredible depth, assuming Umana performs better than he did five years ago for the Galaxy. Grade: B

FC DALLAS. The back line, as well as the whole team, got it together down the stretch at the end of last year with a central pairing of Ugo Ihemelu and converted midfielder George John earning kudos for their play. Former U.S. U-20 Kyle Davies came into the picture as well when he signed with MLS, yet this defense still has much to prove. Grade: C-

SAN JOSE. No team, not even the pathetic Red Bulls, allowed more goals than the 50 that hit the Quakes’ net last season. The health of Jason Hernandez, who played only 16 games because of torn ligaments in his knee and a fractured ankle, is a concern, but if fit, he’s tough enough. Bobby Burling is capable of holding down one spot, Brandon McDonald filled in nicely last year, and rookie Ike Opara showed some upside in limited preseason action. Grade: C-

COLORADO. During the offseason, the Rapids traded Cory Gibbs, who missed significant time battling knee problems and didn’t play all that well when he returned to action. In preseason, Coach Gary Smith used recent Colombian signing Oscar Murillo with Frenchman Julian Gaudet; he also has veteran Drew Moor and a few other options, with the solution yet to emerge. Grade: D